Light strips for lighting and backlighting applications

Abstract

Light strips for emergency lighting, path lighting, accent lighting and device lighting are provided. Devices incorporating and lighted by the light strips are also provided. The light strips include a light emitting layer made from a plurality of semiconductor nanoparticles disposed between and in electrical communication with an anode and a cathode. The semiconductor nanoparticles may be made from Group IV semiconductors, such as silicon. Devices that may be lit with the light strips include displays and keypad, such as those found in cellular phones and personal digital assistants.

1. An electronic device with a lighted keypad, the device comprising a keypad having at least one key, the at least one key incorporating a light strip comprising:
 (a) a first substantially transparent electrode layer; 
 (b) a second electrode layer; 
 (c) a plurality of electroluminescent nanoparticles consisting of quantum confined, crystalline silicon nanocrystals surface treated with an organic or inorganic passivating agent which prevents degradation of the nanoparticles caused by oxygen, said nanoparticles being disposed between the first substantially transparent electrode layer and the second electrode layer, 
 wherein the device further comprises a display lit by the light strip, the light strip providing a single light strip to illuminate both the display and the keypad, and wherein the display is illuminated with light of a higher intensity or light of a different color than the keypad, and wherein the light strip operates without an inverter by switching between an alternating current and direct current voltage source. 
 
     
     
       2. The device of  claim 1  wherein the electronic device is a cellular phone. 
     
     
       3. The device of  claim 1  wherein the electronic device is a personal digital assistant. 
     
     
       4. The device of  claim 1  wherein the electronic device is a watch. 
     
     
       5. The device of  claim 1  further comprising a push-type switch disposed below the at least one key. 
     
     
       6. The device of  claim 1  wherein the display is illuminated with light of higher intensity than the keypad. 
     
     
       7. The device of  claim 1  wherein the display is illuminated with light of a different color than the keypad. 
     
     
       8. A light strip comprising:
 (a) a first substantially transparent electrode layer; 
 (b) a second electrode layer; and 
 (c) a light emitting layer comprising a plurality of electroluminescent nanoparticles consisting of quantum confined crystalline silicon nanocrystals surface treated with an organic or inorganic passivating agent which prevents degradation caused by oxygen, said nanoparticles being disposed between the first substantially transparent electrode layer and the second electrode layer; 
 wherein the light emitting layer comprises nanoparticle density domains along the length of the light emitting layer and the density domains are separated such that a defect in one domain does not affect the remaining domains, further wherein at least two domains have different densities of nanoparticles, and further wherein the light strip operates without an inverter by switching between an alternating current and direct current voltage source. 
 
     
     
       9. The light strip of  claim 8  wherein the light emitting layer comprises a density gradient of nanoparticles along the length of the light emitting layer. 
     
     
       10. The light strip of  claim 8  wherein the size distribution of nanoparticles is non-uniform along the length of the light emitting layer. 
     
     
       11. A lighted electronic device comprising:
 (a) the light strip of  claim 8 ; 
 (b) a display lit by the light strip; and 
 (c) a keypad lit by the light strip. 
 
     
     
       12. The lighted electronic device of  claim 11  wherein the device is selected from the group consisting of cellular phones, personal digital assistants and personal computers. 
     
     
       13. An egress illuminated by the light strip of  claim 8 . 
     
     
       14. A shelf illuminated by the light strip of  claim 8 . 
     
     
       15. The light strip of  claim 8 , wherein the nanoparticles are dispersed in a dielectric medium and the light strip further comprises a dielectric layer disposed between the second electrode layer and the light emitting layer and an insulating layer disposed below the second electrode layer.